Well "anti colonialist" and "freedom fighter" do not a communist make.

Though I can see how a connection could be made that the force fighting an apartheid settler colonial power aligns with anti apartheid anti colonial sentiment.

But critical support is kind of a nuanced thing that usually isn't understood well or interpreted charitably. It often follows the same logic of picking the lesser of two evils as a winning electoral strategy. Which means people end up supporting objectively bad things because they see it defeating an objectively worse thing.